Bug #639118 from Ollie Oldham: archiver should use zipfile before zip

Previously archive_util.py attempted to spawn an
        external 'zip' program for the zip action, if this fails, an
        attempt to import zipfile.py is made...

        This bites folks who have 'old' or non-conforming zip
        programs on windows platforms.  This change tries the 'zipfile'
        module first, falling back to spawning a zip process if
        the module isn't available.